The advent of technology has led to a sea change in the civil engineering construction industry. Foundation support systems for the columns of buildings are characterized by suitable footings based upon the soil condition. A footing is basically an enlarged base for a foundation which is designed to distribute the building load over a larger area of soil and to provide a firm, level surface for constructing the structures. The purpose of the footing is to also provide stability to the structure against swaying or falling due to horizontal forces, such as, for example, high velocity or turbulent winds. In the present invention, the anchors play an important role. The primary function of these anchors is to transmit upward and downward forces, due to column axial load and overturning moments, to the soil at certain depths below the ground.
The depth of the excavation is determined by the structural engineer depending upon the type of soil where the construction is to occur. Surface soil is removed so as to expose the soil that is to be compacted enough so as to bear the load of the column/structure. The depth of the excavation will be just deep enough to place the footings. The footings are poured concrete that help to spread the weight of the structure, walls, piers, columns, light post structures, and the like. The total area of the footings is roughly determined by dividing the total load, including an estimated mass for the footing itself, by the soil bearing capacity.
Concrete is one of the best footing materials because it is hard, durable, and strong in compression. It is easily cast into the unique shapes required for each type of footing. Alternatively, footings can be cast directly within the trench. While this saves the cost of footing forms, care must be taken so that no soil from the sides is mixed in the concrete. Footings can also be piles, bored piers, or of the raft slab type.
Several of the problems being addressed by the present invention is to have the footing that will be light in weight, economical, environmentally friendly, easy to construct, able to be formed relatively quickly, and will require less space as compared to conventional pad type footings. Here the footing forces are resisted by closely spaced deformed steel bars driven into the soil. The steel bars act like mini piles, resisting uplift and downward forces.
In connection with conventional type pad footings, if the vertical loads are relatively small, any overturning moments are resisted by means of the weight of the footing. Hence, it requires large volumes of concrete, more space, more excavation, and more soil disposal. Examples are light posts, substation electrical equipment supports, sign posts, and the like. In accordance with the present invention, the column vertical load and overturning moments are resisted by means of steel bar soil anchors, and by means of their upward and downward load capacity within the soil. The soil anchor footing requires minimum excavation, less soil disposal, is relatively light in weight, requires less space, saves construction time, and provides much higher overturning moment-resistant capacity.
Though the aforenoted conventional and similar systems have been designed to provide certain advantages, they also suffer from various shortcomings. A few of such prior art systems are discussed hereinbelow so as to help distinguish the present invention from such known prior art systems.
U.S. Pat. No. 4,290,245 discloses an earth anchor for embedding the same within the ground and to acquire a secure and snug retention incorporating a shank portion having a helical blade affixed thereto and having a linear cutting edge positioned at a lagging angle off the perpendicular or radius from the shank portion.
Similarly, U.S. Pat. No. 4,742,656 relates to an earth anchor for embedding the same within the ground and incorporating a helical blade(s), having flattened side edges, intervened by rounded or accurate corners, and connecting with its shank for securing with any driving apparatus useful for the power driving of such an earth anchor into the ground.
Both of the anchors disclosed within these prior art patents, however, are expensive and need special machinery to install. They also need a reinforced concrete footing slab to be cast on top of these screw anchors.
In accordance with the present invention, however, steel deformed bars are being used which are readily available, are inexpensive, and are easy to install. The pre-cast type footing in accordance with the present invention can be installed within the ground within a few minutes. As the bars are driven into the ground, they have much higher uplift and downward force resistant capacity than screw type anchors. Furthermore, recycled bars can also be used which will be even cheaper, and moreover, such helps to protect environment since recycled materials are being used. Also, within the soil anchor footing, no additional reinforcement is required within the top slab.
U.S. Pat. No. 5,873,679 discloses a foundation pier adapted to be secured to a support beam of a movable dwelling for supporting the dwelling and for resisting seismic forces applied to the dwelling. It appears that this foundation pier has limitations as to its applications and can be used only for small loads. The present invention, however, is more versatile, can be used for higher loads, and thereby has broader applications.
U.S. Pat. No. 5,924,264 relates to a foundation system comprising a pre-fabricated set of concrete forms for a manufactured building that is already on-site and in-place. The concrete form set includes standard-length sections that bolt together immediately below the rim of the manufactured building. This invention has a specific use like in the case of pre-fab building wall foundations. The present invention, however, discloses a different product and has broader applications.
U.S. Pat. No. 7,308,776 discloses a pole anchor footing system for effectively supporting a post structure within a ground surface. The pole anchor footing system includes a resilient body having a neck portion and a base portion, and an elongate member extending into the body from an upper end of the body. In accordance with the present invention, the footing gets its strength from the anchor bars that are embedded within the ground, while in the prior art, the footing obtains its strength from its pyramidal shape. This has very limited applications when compared to those of the present invention.
U.S. Pat. No. 7,549,259 pertains to a device for creating a footing for a structure including a reinforcing member having a base extending in a first direction, and a leg extending in a second direction, and it is concerned with fence post footings as part of a retaining wall, secured by horizontal anchors. Hence, this device again has limited use. At the same time, the proposed invention is structurally different from the prior art and it also has broader applications.
U.S. Pat. No. 8,037,651 discloses a ground anchor assembly which includes at least two threaded studs, and an anchor plate having at least two openings of appropriate size and shape to receive the at least two threaded studs. The patented system is concerned with installing anchor bolts into concrete in such a way that their alignment is intact. A completely different product is envisaged by the present invention which has broader applications.
Lastly, US 2008/0302028 discloses a ground anchor which comprises an anchoring screw having a screw flight extending around a screw axis wherein the screw flight is generally rigid with some lateral resilient flexibility. This system has the inherent disadvantage of being cumbersome and expensive. But in accordance with the present invention, steel deformed bars are being used which are readily available and are relatively inexpensive. They are also easy to install. The pre-cast type footing in accordance with the present invention can be installed within the ground in one operation and within a few minutes, and is a complete product, as opposed to the prior art system wherein the same requires the casting of a reinforced concrete slab on top of screw anchors.